1. 
[syn: tons, dozens, heaps, lots, piles, scores, stacks, loads, rafts, slews, wads, oodles, gobs, scads, lashings]
2.  storage space in a library consisting of an extensive arrangement of bookshelves where most of the books are stored; 
WordNet (r) 3.0 (2006):
stacks
    n 1: a large number or amount; "made lots of new friends"; "she
         amassed stacks of newspapers" [syn: tons, dozens,
         heaps, lots, piles, scores, stacks, loads,
         rafts, slews, wads, oodles, gobs, scads,
         lashings]
    2: storage space in a library consisting of an extensive
       arrangement of bookshelves where most of the books are stored